Little is known about the evolutionary history of the Molidae because of the fragmentary and largely incomplete fossil record of this morphologically peculiar group of tetraodontiform fishes. The majority of fossils referred to in this family consist of isolated jaws and dermal plates, although a few articulated skeletons are also known. The scarcity of fossils belonging to the Molidae seems to be related to the overall considerable reduction of the bony tissue in the skeleton, with the bones being weakly ossified and characterized by a delicate fibrous or spongy texture. The earliest rare representatives of this family date back to the middle Eocene, while the crown group Molidae appeared in the record no later than the Early Miocene. This chapter illustrates the known fossil record of molids and discusses the phylogenetic relationships between the fossil and extant taxa, and the potential evolutionary drivers that contributed to their diversification.